Experts believe the womb lining is implicated in two-thirds of the implantation failure cases with embryo abnormalities accounting for the rest

A personalised test tuned to the woman's reproductive cycle could benefit many recipients of IVF treatment, going by results from pilot studies.

The scientists at the IVI fertility clinic in Madrid believe that IVF frequently fails because the embryo is transferred into the womb at the wrong time. Less than 24% of the IVF implantations done at present in the UK translate into live births.

The new test looks at the expression of some genes in the cells of the womb lining to pick the best time for implantation.

Clinics currently check the general health of the womb lining using ultrasound.

Prof Juan Garcia-Velasco, of the clinic in Madrid, said: "We think that about 15% of cases of implantation failure are simply due to bad timing."

It is known that there is a two to four-day stretch when the lining, or endometrium, sends out crucial chemical signals that allow the embryo to attach.

This period can vary from woman to woman and for some get shifted earlier or later in the cycle or even be very brief.

In the receptive phase a series of genes switch on and off in a sequence that scientists can read.

In the new test, a biopsy of the endometrium is taken and checked for this gene activity.

"I think it will make a significant difference in the expectations of couples and how we can explain failures," said Garcia-Velasco. "Until now, the endometrium was kind of a black box. Now we can say this was the problem and this is what we can do about it."

He is now leading a clinical trial involving 2,500 patients using the test in more than ten countries, including Britain.

The test is at present done a month before implantation to ensure least disturbance to womb lining at implantation.

The team plans to improvise their method to be less invasive and also closer to implantation time.

Pilot study

In the pilot study, the test was given to 85 women who had each experienced on average five rounds of IVF that had failed at the implantation stage.

The fertile window did not match with the day when the embryo is transferred in standard IVF protocols, the study found.

When the gene analysis was used as a guide, 33% of those treated had a successful implantation.

In the international trial, the test will be offered to women who have had two or more previous instances of implantation failure.

Experts believe the womb lining is implicated in two-thirds of the implantation failure cases with embryo abnormalities accounting for the rest.

Geeta Nargund, medical director of Create Fertility whose London clinic is participating, said: "The weakest link in IVF is implantation failure. I believe this is a breakthrough."

There are more than 60,000 IVF treatment cycles in Britain each year, but just 24% of these lead to live births.